In general, fish changes in quality immediately after their landing with gradual deterioration thereof, and particularly when they are subjected to a treatment by a pressing meat collecting machine the deterioration of freshness occurs abruptly. There is a considerable difference in the degree of deterioration depending on the sort of fish, and the stronger the deterioration is, the poorer the quality will be when produced into a boiled fish paste, and in an extreme case, there may be produced such a minced meat that can not possibly be used for making a boiled fish paste.
Even with the meat of a white meat fish such as pollack, white croaker etc. which has usually been used as a fish suitable for the boiled fish paste, if old or badly treated, it deteriorated in its quality in a moment, so that the resulting minced meat became poor in quality.